Imprinting

Imprinting#

Imprinting ensures shared surfaces between adjacent volumes are meshed consistently. It’s enabled by default.

What is Imprinting?#

When two volumes share a surface (e.g., two boxes touching), imprinting:

  1. Identifies the shared surface

  2. Creates matching mesh elements on both sides

  3. Ensures particles can cross the boundary correctly

Without imprinting, adjacent volumes might have incompatible meshes at their interface, causing particle tracking errors.

Default Behavior#

Imprinting is enabled by default:

model.export_dagmc_h5m_file(
    filename="dagmc.h5m",
    imprint=True,  # Default
)

Disabling Imprinting#

For geometries that don’t need it:

model.export_dagmc_h5m_file(
    filename="dagmc.h5m",
    imprint=False,
)

When to Disable Imprinting#

Safe to disable when:

  • Single volume geometry

  • Volumes don’t touch (separated in space)

  • All volumes are independent (no shared surfaces)

Keep enabled when:

  • Adjacent volumes share surfaces

  • Volumes are in contact

  • You’re unsure

Performance Considerations#

Imprinting can be computationally expensive for complex geometries with many touching volumes. Disabling it may speed up mesh generation, but only do so if you’re certain volumes don’t share surfaces.

Imprinting and Material Tag Order#

Imprinting may change the internal ordering of volumes. cad_to_dagmc handles this automatically, preserving the correct material tag assignments.

If you’re using volume IDs in set_size or unstructured_volumes, be aware that imprinting may affect the volume numbering. Using material tag names instead of IDs is more robust.

Example: Adjacent Boxes#

import cadquery as cq
from cad_to_dagmc import CadToDagmc

# Two boxes sharing a face
box1 = cq.Workplane("XY").box(10, 10, 10)
box2 = cq.Workplane("XY").moveTo(10, 0).box(10, 10, 10)  # Adjacent to box1

assembly = cq.Assembly()
assembly.add(box1)
assembly.add(box2)

model = CadToDagmc()
model.add_cadquery_object(assembly, material_tags=["mat1", "mat2"])

# Imprinting ensures the shared face is meshed consistently
model.export_dagmc_h5m_file(
    filename="dagmc.h5m",
    imprint=True,  # Important for adjacent volumes
)

See Also#

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